1. Field of the Invention
The present invention relates to a control apparatus for a hybrid vehicle. In particular, the invention relates to a control apparatus for a hybrid vehicle that can quickly respond to an assistance request by a driver at the time of vehicle departure.
2. Description of the Related Art
Heretofore there is known a hybrid vehicle incorporating a motor in addition to an engine as drive sources for vehicle propulsion.
One type of such a hybrid vehicle is a parallel hybrid vehicle where the drive output from the engine is assisted by the motor. In this parallel hybrid vehicle, for example at the time of acceleration, the drive output from the engine is assisted by means of the motor, while at the time of deceleration, various control is carried out such as performing battery charging by deceleration regeneration, so that the remaining battery charge can be maintained while satisfying the requirements of the driver (for example as shown in Japanese Unexamined Patent Application, First Publication No. Hei 7-123509).
In the above-mentioned hybrid vehicle, in the case where assistance is required in response to the acceleration intention of the driver, the output from the engine is drive assisted by the motor. However, for the acceleration intention of the driver there are various aspects depending on operating conditions. For example, there is the case where immediately after departure from a stopped condition, the driver depresses the accelerator pedal in order to accelerate, or the case where while traveling, the driver depresses the accelerator pedal in order to accelerate.
Incidentally, compared to the case of accelerating while the vehicle is traveling, in the case where immediately after departure, the driver depresses the accelerator pedal in order to accelerate, if there is not a rapid response to the acceleration intention of the driver, the driver suffers an unpleasant sensation. Especially, in the case of a hybrid vehicle which incorporates an automatic transmission, this becomes a problem in that it is not possible to avoid imparting a sluggish feeling with respect to the acceleration intention of the driver, by the amount that the power is transmitted via the automatic transmission. Therefore, there is a problem in that the driver depresses the accelerator pedal more than necessary, and as a result this is adverse to improvement in fuel consumption.
It is an object of, the present invention to provide a hybrid vehicle control apparatus, wherein an unpleasant sensation is not imparted to a driver depressing an accelerator pedal at the time of departure.
To solve the above-mentioned problems, the present invention is a control apparatus for a hybrid vehicle with an engine (for example, engine E in the embodiment) and a motor (for example, motor M in the embodiment) as the drive sources of the vehicle, and a power storage unit (for example battery 3 in the embodiment) for storing electrical energy from the output of the engine or a part of the kinetic energy of the vehicle which has been converted by the motor, and an automatic transmission (for example the automatic transmission (CVT) T in the embodiment), comprising: a charge condition detection section (for example battery ECU 31 in the embodiment) which detects the charge amount of the power storage unit and determines a mode including at least a charge and discharge permit mode which permits charge and discharge of the power storage unit, and a discharge suppression mode which permits charge and suppresses discharge of the power storage unit; and an assistance determination section (for example the motor assistance determination flag F_MAST in the embodiment) which determines whether or not to perform driving force assistance for the engine by the motor, wherein the assistance determination section has at least a departure assistance determination section (for example the departure assistance request flag F_MASTSTR in the embodiment) which determines departure assistance that performs driving force assistance by the motor at the time of departure of the vehicle, and an acceleration assistance determination section (for example the throttle motor assistance determination flag F_MASTTH in the embodiment) which determines acceleration assistance that performs driving force assistance by the motor at the time of acceleration of the vehicle, and the departure assistance determination section determines to not permit assistance in the case where the charge condition detection section determines the discharge suppression mode (for example step S353 and step S364 in the embodiment) and determines discharge suppression time permit determination (for example step 360 and step 358 in the embodiment) which permits assistance in the discharge suppression mode, and in the case where driving force assistance by the motor is permitted by the discharge suppression time permit determination, the departure assistance is performed by the motor even in the discharge suppression mode. By having such a construction, then even in the case of the discharge suppression mode due to the remaining charge of the power storage unit being low, the acceleration intention of the driver at the time of departure is precisely reflected, so that the vehicle can depart quickly. Therefore, there is the affect that the unpleasant sensation due to tardiness at the time of departure is not imparted to the driver.
In the present invention, the discharge suppression time permit determination by the departure assistance determination section, determines a degree of throttle opening corresponding to an acceleration intention of a driver (for example step S363 in the embodiment), and permits the departure assistance in the case where the degree of throttle opening corresponding to the acceleration intention exceeds a predetermined determination threshold value (for example determination threshold value #THSTRC in the embodiment) which is greater than a departure assistance determination threshold value (for example determination threshold value #THSTR in the embodiment) for at the time of the charge and discharge permit mode. By having such a construction, in the case of the discharge suppression mode, the departure assistance is permitted only in the case where a degree of throttle opening larger than a determination threshold value for at the time of the charge and discharge permit mode, is detected. Hence the discharge amount of the power storage unit can be suppressed to a necessary minimum. Therefore there is the affect that in the discharge suppression mode, a rapid departure corresponding to the acceleration intention of the driver becomes possible, while keeping a drop in the remaining charge of power the storage unit to a minimum.
In the present invention, an assistance amount for the departure assistance in the discharge suppression mode may be determined by a degree of throttle opening or a depression amount of an accelerator pedal. By having such a construction, it is possible to obtain a necessary departure assistance amount from immediately after departure, determined by the degree of throttle opening or the accelerator opening. Therefore, there is the affect that the engine can be quickly assisted corresponding to the accelerator operation by the driver.
In the present embodiment, the assistance determination section may determine the departure assistance when, based on at least engine speed (for example engine speed NE in the embodiment) and vehicle speed (for example vehicle speed VP in the embodiment), the engine speed is less than or equal to a predetermined value (for example departure assistance execution upper limit value #NSTRAST in the embodiment), and the vehicle speed is less than or equal to a predetermined value (for example assistance execution upper limit vehicle speed #VSTRAST in the embodiment). By having such a construction, departure assistance can be executed only at the time of departure. Therefore, there is the affect that a reduction in the remaining charge of the power storage unit due to departure assistance can be kept to a minimum.
In the present invention, in the case where the charge condition detection section determines the discharge suppression mode, the acceleration assistance determination section may determine that the driving force assistance by the motor is not performed. By having such a construction, drive assistance by the motor in the discharge suppression mode can be limited to at the time of departure. Therefore, further reduction in the remaining charge of the power storage unit can be suppressed, so that this does not cause a problem from the point of energy management.
In the present invention, an assistance amount for the departure assistance in the discharge suppression mode may be a constant value (for example assistance value #STRASTCC in the embodiment). By having such a construction, assistance at the necessary assistance amount from immediately after opening the accelerator can be ensured.